In polish and coatings applications where durability and toughness are important, polymers employing metal ions as crosslinking agents have traditionally been used. These metal containing polymers allowed the formulator to produce polish and coatings compositions with all necessary formulation ingredients in a single-package system. The single-package system allows the formulator to use the coating at the site without additional mixing and preparation, and at a lower cost, when compared to multi-package compositions. More recently, however, metal containing coatings have come under extreme pressure from both federal and state governments due to environmental concerns. In an attempt to address these concerns, formulators are demanding from raw material suppliers, polymers which provide equivalent performance without the use of metal ions. In response to the environmental concerns, formulators have increased their use of non-metal containing, single-package emulsion polymer systems.
However, when single-packaged emulsion polymers are cured under ambient conditions, and their performance is compared to metal-containing polymer systems, emulsion polymers suffer inherent shortcomings with respect to durability, toughness and resistance, such as, for example, pad induced scratching from floor machine maintenance procedures. Therefore, aqueous-based, non-metal containing coatings have not found wide acceptance in polish and coating applications where strength, durability and toughness are important. Another shortcoming of aqueous-based no metal containing systems is the need for multiple package systems in order to obtain the equivalent performance of a metal-containing system. Multiple package systems require the end-user to mix components just prior to the coatings application. Often, the use of multiple package systems are impractical and the formulator fails to obtain a proper mix of the components, resulting in coatings that are deficient in properties such as removability of the coating for cleaning purposes.
It is generally known that incorporation of silane functionality into a polymer can yield compositions which self-crosslink at ambient temperature or about 25.degree. Centigrade. Crosslinking occurs due to the facile hydrolysis of alkoxysilane groups to silanols and their subsequent condensation to form Si--O--Si linkages in the presence of water (See e.g., Feasibility of Using Alkoxy Silane Functional Monomers for the Development of Crosslinking Emulsions, T. R. Bourne, B. G. Bufkin, G. C. Wildman and I. R. Grave in the Journal of Coatings Technology, Vol. 54, No. 684, Jan. 1982). However, because of the ease of hydrolysis and subsequent condensation of the silane functionality, there has been a continuing and most difficult problem in producing stable silicone-modified waterborne polymers in a single-package system.
What we have found to be novel and unanticipated is a waterborne or water dispersed polymer system which solves the environmental concerns of traditional metal-containing systems. The waterborne system of the present invention cures at ambient temperature, is formulated as a single-package system, is environmentally friendly since it is void of metal ions, and in spite of being aqueous based, is durable, tough and detergent-resistant with removability characteristics that are equivalent to metal ion-based polymer systems.
Furthermore what we have found to also be novel and unanticipated is that the performance of metal containing polymers can be improved by modifying the polymer with silane functionality.
This is accomplished by post-reacting an acetoacetoxy-functional polymer with an amine-functional silane. Coatings produced from the emulsion polymers of the present invention are especially useful for applications to flooring and wall substrates.